1. Field of the Invention
This invention relates to a conveyor consisting of an indefinite sequence of interconnected links having a nonskid top surface for support of the objects to be conveyed. This invention also relates to a method for manufacture of the conveyor links.
2. State of the Prior Art
The problem of making conveyor belts or chains suited to running along appropriate guides and that at the same time have a skidproof support surface on which are arranged the objects to be conveyed in the horizontal plane or in a sloped direction relative to said plane has long been known in the conveyor field.
To solve this problem, conveyors consisting of an indefinite sequence of interconnected modular members like chain links to which is applied a covering of malleable skidproof material on the entire surface or partially thereon have been proposed. The members or links are made of rigid thermoplastic material and are provided with undercuts designed to receive in engagement a portion of the malleable material to anchor the skidproof covering to the conveyor belt. For example, in patent No. EP 0 523 810 it is proposed to form a reticulate structure on which is molded the malleable material and that is then fastened to the modular member of the conveyor. The reticulate structure is made of a material suited to being welded (for example with an ultrasonic weld) to the material used to make the modular members making up the conveyor. This solution, while avoiding the use of sophisticated and costly molds for forming the undercuts, implies a sequence of molding and welding steps that make the conveyor manufacturing process slow and uneconomical.
According to the conventional and well known methods of overmolding malleable or thermoplastic materials, it could be thought to hot mold the malleable material forming the covering directly on the rigid link of the conveyor without the latter having undercuts for anchoring the covering. To do this, it is necessary to use malleable material compatible with the rigid material of the linked modular-member body to obtain a link effect by thermal effect. However, the most suitable rigid thermoplastic materials to be used for making the modular members of the conveyors are not generally compatible with the rubbery substances that have good skidproof properties. In addition to this, even with compatibility between the two materials the fastening realized does not ensure satisfactory and safe mechanical resistance so that the skidproof covering could detach itself in the long term from the body of the link during use of the conveyor. It is clear that unreliability of this type is a considerable disadvantage.
In addition, to obtain a strong link with the interface between the two materials it is to be hoped that the surface of the body of the link at least reach softening with resulting alteration of its dimensional characteristic and deterioration of the quality obtained in molding.
The general purpose of this invention is to remedy the above mentioned shortcomings by making available a conveyor having a skidproof surface economical and simple to manufacture.
Another purpose of this invention is to make available a conveyor that would ensure a firm and steady fastening of the skidproof portion to the modular linked members forming the conveyor.
Another purpose of this invention is to make available a method for manufacture of linked members of a conveyor that would be fast and economical.